Rennet

Rennet, the stomach contents of an unweaned animal; also, the membrane lining the stomach. The word rennet also refers to preparations that contain the enzyme rennin and that are used in curdling milk. The chief source of rennet is the fourth stomach of young calves. Rennet is used in making cheese, junket, and medicinal preparations. It is also used to coagulate casein (a milk protein) in making plastics.

With its long legs and goofy way of motoring about, the daddy longlegs generally doesn't top lists of the scariest spiders. But should it? After all, if legends are to be believed, it's one of the most poisonous spiders of all.